The present invention relates to an improved method and apparatus for monitoring intravenous drips.
Intravenous drips are frequently used to administer a continuous flow of fluid to a patient over a given period of time. The drip may administer saline solution to the patient to prevent dehydration and increase blood volume or other fluids, such as insulin, blood or gelofusin. The intravenous drip has a bag containing the fluid which is attached to a filter chamber. This leads to a reservoir which has a piece of tubing extending therefrom which feeds fluid through a needle into the vein of a patient.
The drips are checked at regular intervals by nursing staff to ensure that the fluid is still flowing through the apparatus into the patient. This is time consuming for the nursing staff and additionally, results in the patient being disturbed during the night when the nurse has to check that the drip is still working correctly. Some essential fluids are pumped into the patient via the intravenous drip to ensure that the correct amount of fluid is being administered but the majority of fluids enter by means of gravity, with the bag of fluid being positioned above the height of the patient such that the fluid drips down the tubing and is delivered into the vein of the patient. This necssitates carefuil monitoring of the drip by nursing staff to ensure that sufficient fluid is being administered to the patient.
One direct injection pump is that marketed under the name I-VAC(trademark) which uses a pericycle pump to administer a measured amount of fluid to the patient. This type of pump ensures that the fluid is delivered in the correct dosage to the patient but is only used in life threatening situations for the delivery of essential fluids. This type of pump is expensive and therefore not readily available for use with all patients and furthermore, is very heavy. This is obviously undesirable because the apparatus must be taken with the patient when leaving his hospital bed. The pump is also unsuitable for use in certain departments of the hospital, such as the radiography department,
U.S. Pat. No. 4,321,461 (KJW/D Associates) describes a flow rate monitor and totalizing count display apparatus that uses a pulsed infrared light source and receiver and include alarm means for signalling a no-drop condition and for signalling when a preselected count is reached. WO 96/17637 (Midex Marketing Limited) relates to an intravenous infusion flow rate monitoring device that includes a programming console with a data input unit for inputting infusion parameters. The device also includes an alarm unit for indicating when the desired parameters are not being met. However, whilst these devices work effectively they are complex and therefore expensive. They are also difficult and time-consuming to operate.
It is an aim of the present invention to provide a method and apparatus for monitoring the flow of fluid through an intravenous drip which is lightweight and relatively cheap to manufacture.
It is a further aim of the present invention to provide a method and apparatus for monitoring the flow of fluid through an intravenous drip thereby removing the need for a nurse to frequently check the drip to ensure that the fluid is being administered to the patient.
Yet a further aim of the present invention is to provide a method and apparatus for monitoring the flow of fluid through an intravenous drip which has no detrimental effect on the fluid administered and does not interfere with other equipment which may be operating in the vicinity of the apparatus
Accordingly, a first aspect of the present invention provides a method for monitoring the flow of fluid through an intravenous drip comprising the steps of transmitting a signal through a fluid flow passage, detecting the signal transmitted through the passage, monitoring the rate of flow of fluid through the passage from detection of said signals, characterised by the step of setting activation of an audible or visible indicator at a rate corresponding to the rate of flow of fluid through tie passage once a constant rate of flow is achieved wherein detection of a flow rate above and/or below the constant rate activates said indicator.
According to a second aspect of the present invention there is provided an apparatus for monitoring the flow of fluid through an intravenous drip comprising a signal transmitter for tansmitting a signal through a fluid flow passage, a sensor for detecting the signal transmitted through said passage, monitoring means for monitoring the rate of flow of fluid through the passage from detection of signals by said sensor and at least one visible or audible indicator for indicating when the flow rate rises above and/or falls below a constant rate characterized in that the monitoring means includes means for setting activation of said indicator upon achievement of said constant rate.
The signal used in the method and apparatus of the present invention may be infra-red light produced from an infra-red emitter. Alternatively, a red or other light source may be used. Preferably, this signal is transmitted to the intravenous drip by means of an optical fibre. A through-scan, in the form of a bracket, is preferably provided for placement around a region of the intravenous drip for allowing transmission of the beam across the passageway of the flow of fluid. A further optical fibre is preferably attached to the opposite side of the through-scan to receive the signal transmitted through the passage and deliver the signal to the sensor.
The through scan in the form of a bracket is preferably hinged to allow easy placement around a region of the intravenous drip, such as the chamber or drip pod. Adjustable fastenings may be provided to fasten the bracket around the intravenous drip. The bracket may be made of any suitable material but preferably is made of a lightweight plastics material. More preferably, the through-scan is in the form of a C-shaped bracket which is provided with a living hinge to allow the opening in the bracket to be expanded to fit around a region of the intravenous drip and then relaxed such that the bracket grips the drip. Preferably, the C-shaped bracket is provided with two arms extending from the rear thereof, opposite the opening, which may be pressed together to cause divergence of the free ends of the C-shaped bracket. The arms are preferably provided with gripping means on their outer surface. The bracket and arms may be produced as a single moulded plastics unit.
Preferably, a housing, for example in the form of a pocket-sized box is provided for the electronic circuitry, sensor and infrared emitter. The housing is preferably made of a lightweight plastics material. Preferably, the sensor is linked to an indicator in the form of a light emitting diode (LED) which becomes illuminated when the flow of fluid stops. It is preferable that the light emitting diode is visible through the box. Alternatively or additionally, the sensor may be linked to an audible alarm.
In a preferred embodiment of the present invention, the sensor is linked to a bicolour LED which emits a green light when fluid is flowing through the apparatus and changes to a red light when the flow of fluid stops for a predetermined period of time. This change may be achieved when the sensor receives a predetermined amount of energy within a given period of tune indicating that the infra red signal has not been broken by fluid flow. Preferably, the timing is adjustable. The green light may flash with each drip of fluid that passes through the intravenous drip to confirm that the apparatus is working correctly.
Altematively or additionally, the sensor may be linked to suitable electronic circuitry to allow the number of drops of fluid which are fed from the intravenous drip within a set period of time to be determined, for example drops per minute. Preferably, the number of drops which pass through the apparatus within the set period of time is visible on a display units such as a liquid crstal display (LCD) LED unit provided on the housing or elsewhere.
More preferabley still, the housing is provided with a indicator to demonstrate that fluid is flowing through the drip and a separate display unit, such as an LCD which illustrates the rate of flow of fluid passing through the apparatus. Preferably, the indicator emits a specified colour or other sign when the apparatus is detecting a rate within a specified range of the preset value corresponding to the constant rate. Preferably, the indicator will change to another colour or different sign if the number of drops detected falls below or rises above a predetermined tolerance level, such as xc2x150% of the preset value corresponding to the constant rate. The indicator may also undergo a corresponding change if no drops are detected within a given period of time.
The apparatus may be powered by means of a battery or mains supply. Preferably, a battery is provided in the housing together with a battery recharger which may be linked to the mains supply. A tricolour LED may be included in the apparatus in place of a bicolour LED, with the third colour of light indicating when the battery is low. Alternatively, a separate indicator may be provided, for example, on the housing, to indicate when the battery is low. The housing is preferably provided with a clip or hook for attachment to the patient, drip stand or elsewhere.
The indicator may also comprise a beacon positioned by the patient or at a nursing station which lights up when the flow of fluid has stopped for a given period of time. Preferably, the beacon is provided on the top of a tall stand. Alternatively, or additionally, a wire may extend from the optical fibre to a glass bulb or light emitting diode which may be placed for example at the top of the drip or drip stand to provide increased visibility of the indicator. The sensor may also be linked to a computer monitor at a nursing station.
The housing may be linkable to an extension lead which may be attached to the optical fibre lead, for example by means of a screw mechanism, to allow an intravenous drip having the through-scan attached thereto to be remote from the housing. This is particularly desirable for when a patient is entering a high risk area, such as a scanning area, whereby the housing may be left outside the area. A receiver, preferably wall mounted, may be provided outside the area for storage of the housing and to allow the drip to be monitored whilst the patient is in the high risk area.
The method and apparatus of the present invention may further provide means for monitoring the amount of fluid which has been administered to a patient. The amount of light which passes through a drop of fluid and the number of drops counted by the sensor within a given period of time may be used to establish the volume of fluid administered, using appropriate calibrations for particular fluids, for example, the number of ml administrated per hour. The volume per hour may be displayed on a display unit, such as an LCD unit provided on the housing or elsewhere. A computer may collect data for a large number of intravenous drips which may be displayed on a computer screen.